Drive system for domestic appliances

ABSTRACT

A drive system for a domestic appliance provides inner and outer coaxial drive outlets operative at different speeds and comprises an active limb, which incorporates an electric drive motor and a shaft driven by said motor and coupled to the inner drive outlet to drive it at a selected speed. The system also includes a passive limb which incorporates a rotary component; the two limbs being mounted in fixed relationship to one another. A first speed reduction mechanism couples the shaft to the rotary component of the passive limb and a second speed reduction mechanism couples the said rotary component to the outer drive outlet. Conveniently, the rotary component comprises a further shaft, disposed substantially parallel to the driven shaft of said motor, and both limbs of the system are rigidly mounted to, and supported by, a common framework of support members. Both speed reduction mechanisms are typically belt driven, and may provide identical reductions.

FIELD OF THE INVENTION

This invention relates to drive systems for domestic electricalappliances, and especially though not exclusively to such systems forkitchen appliances such as food processors.

BACKGROUND OF THE INVENTION

Drive systems for kitchen appliances are required to fulfill manycriteria, which critically influence various aspects of their design andconstruction and, in many cases, present the need for compromise. Forexample a single appliance, such as a food processor can be required toperform tasks which dictate the ability to operate with widely varyingspeed/torque characteristics, and such performance has to be achieved ina reliable and user-friendly manner, without the generation of undueamounts of noise and/or vibration, in a relatively inexpensive applianceof compact dimensions, of which the operating height is of particularconcern.

Many drive systems have been adopted in efforts to optimise the overallperformance/price/configuration package offered to the consumer, butmost have fallen short of the ideal requirements, at least in somerespects.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a drive system for adomestic appliance, which system adopts an approach to the basic drivelayout which enables at least one of the criteria mentioned above to beaddressed from a novel perspective.

According to the invention from one aspect there is provided a drivesystem for a domestic appliance, the system providing inner and outercoaxial drive outlets operative at different speeds and comprising afirst limb, incorporating an electric drive motor and a drive shaftdriven by said motor and coupled to said inner drive outlet to drive itat a selected speed, and a second limb including a rotary component, thelimbs being disposed and maintained in spatially fixed relationship toone another; a first speed reduction mechanism coupling the drive shaftto the rotary component of the second limb and a second speed reductionmechanism coupling the said rotary component to said outer drive outlet.

Preferably, said rotary component comprises a further shaft disposedsubstantially parallel to the drive shaft of said motor, whereby both ofsaid first and second speed reduction mechanisms can be directlyconnected between said shafts, giving positive driving capability andpermitting the construction to be dynamically balanced to reduce wearand to control noise and vibration, even when the system is operatedunder adverse conditions.

Both limbs of the system are preferably rigidly mounted to, andsupported by, a common framework of support members to promote robustand smooth operation.

According to the invention from another aspect there is provided a drivesystem for a domestic appliance, the system comprising a first limbincluding an electric motor having a drive shaft provided with acoupling intended to provide a first drive outlet operative at aselected speed, and a second limb including a further shaft disposedsubstantially parallel to the drive shaft and offset therefrom, a firstspeed reduction mechanism coupling the motor to the further shaft and asecond speed reduction mechanism coupling the further shaft to a seconddrive outlet concentric with the first drive outlet, and wherein rigidmounting means is provided to mount the two shafts in said substantiallyparallel relationship to one another.

The incorporation of the motor directly into one of the operative limbsadvantageously imparts rigidity into the drive system as a whole.

The selected speed can, in accordance with either aspect of theinvention, conveniently be the operational speed of the motor, and istypically in the range 10,000 to 20,000 rpm.

Preferably, in accordance with either aspect of the invention, the motoris a series motor of short axial length, measured along the drive shaft,which permits the height of the drive system, and therefore of theappliance as a whole, to be kept acceptably low, with the drive shaftsdisposed upright.

Preferably, in accordance with either aspect of the invention, thecoaxial drives operate respectively at high speed, direct from themotor, for blending purposes, and at a lower speed suitable for foodprocessing.

It is further preferable, as regards either aspect of the invention,that the speed reduction mechanisms comprise respective belt and pulleymechanisms disposed parallel to one another. This provides reliable andcost-effective speed reduction without unduly increasing the axiallength, thus the operative height, of the overall system.

Where two belt and pulley mechanisms are employed they can, if desired,be configured to impart identical speed reductions, thus permittingduplicate components to be used; allowing economies of scale to be takeninto account and increasing the cost effectiveness of the system.

More preferably still, as regards either aspect of the invention, thespeed reduction mechanisms are respectively disposed to either side ofthe motor in an axial direction, (above and below the motor respectivelyin operation) thus providing a stable system with good sound andvibration performance.

The system may, in some embodiments, comprise first and second mountingplates, disposed parallel to one another and on opposing sides of (aboveand below respectively) said motor, in the axial direction. In thesecircumstances it is preferred that the first and second speed reductionmechanisms are disposed respectively below the second mounting plate andabove the first mounting plate.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be clearly understood and readilycarried into effect, particular embodiments thereof will now bedescribed, by way of example only, with reference to the accompanyingdrawings, of which:

FIG. 1 shows, in perspective view and with the casing partially cutaway, a drive system in accordance with one example of the invention andshowing a blender drive outlet,

FIG. 2 shows, in similar view to FIG. 1, the system with a foodprocessor drive shaft in place, masking the blender drive outlet, and

FIG. 3 shows, in similar view to FIG. 1, a drive system in accordancewith a second, and preferred, embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, there is shown in part the base casing 1 of afood processor generally indicated at 2. The processor incorporates,within the casing 1, a series motor 3 mounted with its drive axis 4vertical; the motor having a drive shaft 5 extending both upwardly anddownwardly therefrom, along axis 4, and journalled in respectivebearings (not shown) carried by upper and lower mounting plates 6, 7.

The motor 3 drives directly by way of its shaft 5 a first drive outlet13 which constitutes, in this example, a blender drive outlet thatoperates, of course, at full motor speed. Also journalled in respectivebearings, shown schematically at 8 and 9, in the plates 6 and 7 is asecond shaft 10, parallel to the drive shaft 5. The shaft 10 is driven,via a first speed reducing drive mechanism 11, by the motor 3 and thenitself drives, via a second speed reducing mechanism 12, a relativelylow speed drive outlet 14 which is concentric with the drive outlet 13and is intended to provide, via a detachable bowl drive shaft 15 (seeFIG. 2) a food processor drive. This latter drive operates at a speedthat is less than the motor speed by an amount determined by the firstand second speed reducing drive mechanisms 11 and 12.

In this example, both speed reducing mechanisms comprise belt and pulleysystems, and are dimensioned and configured such that each provides aspeed reduction of 3.33:1, causing the overall speed reduction asbetween drive outlets 13 and 14 to be approximately 11:1 though theactual values of reduction used are at the designer's discretion. Thereis, however, merit in having one speed reducing mechanism duplicate theother, as this permits economies of scale to be made in obtainingpulleys and belts (or other components if different mechanisms areused).

In detail, the speed reducing mechanism 11 comprises a small pulley,part of which is visible at 16 and which is directly mounted to thedownward extension of the motor drive shaft 5, a relatively large pulley17 directly mounted to the shaft 10, and a drive belt 18. Likewise, thesecond speed reducing mechanism 12 comprises a relatively small pulley19 directly mounted to the shaft 10, a relatively large pulley 20directly coupled to the food processor drive outlet 14 and a drive belt21. As previously indicated, if the speed reductions imparted by the twomechanisms 11 and 12 are to be the same, the smaller pulleys 16, 19; thelarger pulleys 17, 20 and the belts 18, 21 respectively can usefully beduplicates.

In this example, and preferably, the speed reducing mechanism 11 ismounted just below the lower mounting plate 7, whereas the speedreducing mechanism 12 is mounted just above the upper mounting plate 6;the plates 6 and 7 being rigidly mounted to the casing 1. By this means,there is provided a rigid assembly comprising parallel drive shafts, orlimbs, one of which incorporates the motor 3. This provides naturalstrength and rigidity in a cost-effective and compact manner, andprovides moreover a basic platform or module which is capable with minormodifications of use in various forms of kitchen appliance.

FIG. 2 is identical to FIG. 1, except that it shows the detachable bowldrive shaft 15 attached to the food processor drive outlet 14.

It will be appreciated that the detailed configuration of the drivesystem will vary in dependence upon various parameters of the overallappliance design and its operating criteria. For example, instead ofusing separate upper and lower plates 6 and 7 to achieve the rigidmounting of the motor and the other dynamic components of the system,extensions of the cast motor end frames can be used. Also, although aspeed reduction of 11:1 has been referred to in the specific exampledescribed above, different ratios can be used, though a reduction in therange of 10:1 to 12:1 is favoured in a system providing blender and foodprocessor drives as described above. Furthermore, the reductions imposedby the two mechanisms 11 and 12 need not be the same.

In one practical example, the centre distance between the shafts 5 and10 was 81.6 mm, though this is not a critical dimension and variantshave been made with the offset as low as 49.0 mm. In the embodiment ofthe invention to be described with reference to FIG. 3, the offset incurrent use is 56.55 mm.

Referring now to FIG. 3, wherein components common to FIGS. 1 and 2carry the same reference numbers and will not further be describedexcept insofar as they are differently configured and/or inter-relate toother components, a principal difference from the embodiment shown inFIG. 1 is the omission of the lower mounting plate 7. The components inFIG. 3 are all supported from the upper mounting plate 6 which issuspended, by any convenient fixture components, such as screws (notshown) passing through grommeted apertures such as 22 in the mountingplate 6, from an upper inside surface of a suitable casing (not shown).More sophisticated antivibration mounts than grommets may be utilisedfor the mounting of the plate 6 if desired. Indeed, active sensors suchas piezo-electric washers, may be employed to provide electrical signalsindicative of out-of-balance forces such as may be caused by employingthe appliance incorporating the drive system of the invention for someinappropriate purpose. The signals from any active sensors employed canbe processed appropriately, for example by a microprocessor unit, togenerate audible and/or visual warnings, or to automatically shut downthe system in response to out-of balance forces in excess of permittedthreshold levels.

The drive system is, in this embodiment of the invention, suspended fromthe plate 6 by way of a common supportive framework comprising lower andupper die-cast, U-shaped end frames 23, 24 which are respectivelysecured to the lower and upper surfaces of the laminations of the motor3. Each end frame is formed with a respective girder-like extension 23a, 24 a, which extensions provide a rigid mounting for the shaft 10. Theend frames 23 and 24 incorporate, as will be appreciated, respectivelower and upper bearings for the shafts 5 and 10, and in generalconstitute a framework that rigidly supports the components of thesystem and maintains them in their desired spatial relationship. FIG. 3also shows the blades such as 25 of a cooling fan mounted axially withthe motor 3; though it will be appreciated that alternative fanconstructions may be used and indeed, in some operating environments, nofan may be needed. A brush board for the motor is shown at 26.

In this embodiment, unlike that of FIGS. 1 and 2, the reductionsimparted by the first and second speed reduction mechanisms differ fromone another. Here, the pulleys 16 and 17 have 15 and 71 teethrespectively whilst the pulleys 19 and 20 have 27 and 72 teethrespectively. These particular parameters have been found to operatewell in the system configuration of FIG. 3 although of course the actualarrangements used may differ in any given embodiment as a result ofdesign, economic and/or functional demands.

In general it will be seen that the invention utilises first and secondoffset limbs, one active in the sense that it contains the drive motor,and the other passive, in the sense that it is driven only from theactive limb; the two limbs being linked by a pair of speed reductionmechanisms to permit coaxial drives to be derived from the active limb.

Although belt-driven drive mechanisms have been shown and describedherein, and indeed are preferred from many operational perspectives,other drive mechanisms can be used if preferred, notably those, such asepicyclic gearboxes, that can be configured into a shallow envelope andthus do not compromise the beneficially modest operating height of thesystem.

Using the drive system described herein as a basic module, it ispossible with relatively simple design modifications to change driveratios and/or drive outlet locations. Moreover, extra drive outlets canbe readily incorporated and their desired relative operational speedsreadily contrived.

If preferred, moreover, the system can tolerate both speed reducingmechanisms being mounted, in close proximity to one another, adjacenteither the upper mounting plate 6 or (if provided) the lower mountingplate 7.

Additional drive outlets can be provided from the system if desired, andmotion therefor can be derived from any convenient point in the system.For example, one or more further drives can be taken, directly orindirectly, from the shaft 10 in the passive limb of the system; usebeing made of known direction-changing mechanisms if necessary toprovide any outlet that needs to be out of line with the shaft 10.

While various descriptions of the Present invention are described above,it should be understood that the various features can be used singly orin any combination thereof. Therefore, this invention is not to belimited to only the specifically preferred embodiments depicted herein.Further, it should be understood that variations and modificationswithin the spirit and scope of the invention may occur to those skilledin the art to which the invention pertains.

Accordingly, all expedient modifications readily attainable by oneversed in the art from the disclosure set forth herein that are withinthe scope and spirit of the present invention are to be included asfurther embodiments of the present invention. The scope of the presentinvention is accordingly defined as set forth in the appended claims.

What is claimed is:
 1. A drive system for a domestic appliance; thesystem comprising a base casing containing: an electric drive motor, afirst drive shaft driven by said motor, said first drive shaft extendingaxially of said motor and in both directions therefrom; a second driveshaft offset with respect to said first drive shaft and substantiallyparallel thereto; a first speed reduction mechanism coupling the firstdrive shaft to the second drive shaft; a supporting framework configuredto dispose and maintain said first and second drive shafts in spatiallyfixed relationship to one another; said framework including mountingcomponents disposed axially to both sides of said motor for each of saiddrive shafts; and said mounting components including respective bearingsfor said first and second drive shafts; the system further includingfirst and second drive outlets upstanding from said casing; said firstand second drive outlets being coaxial and configured with one of saiddrive outlets surrounding the other said drive outlet; and a couplercoupling said first and second drive shafts respectively to said firstand second drive outlets to drive said drive outlets in rotation withsaid first drive outlet being driven at a preselected speed; the couplerfurther comprising a second speed reduction mechanism coupling saidsecond drive shaft to said second drive outlet.
 2. A system according toclaim 1 wherein the motor is a series motor of short axial length,measured along the drive shaft.
 3. A system according to claim 1 whereinthe first drive outlet provides a relatively high speed drive configuredto facilitate its use for blending purposes, and the second drive outletprovides a relatively low speed drive configured to facilitate its usefor food processing.
 4. A system according to claim 1 wherein the speedreduction mechanisms comprise respective belt and pulley mechanismsdisposed parallel to one another.
 5. A system according to claim 1wherein the two belt and pulley mechanisms impart identical speedreductions.
 6. A system according to claim 1 wherein the speed reductionmechanisms are disposed to either side of the motor in an axialdirection relative thereto.
 7. A system according to claim 1 comprisingfirst and second mounting plates disposed parallel to one another and onopposing sides of said motor, in an axial direction relative thereto. 8.A system according to claim 7 wherein the first and second speedreduction mechanisms are disposed respectively below the second mountingplate and above the first mounting plate.
 9. A drive system according toclaim 1 wherein said preselected speed is the operational speed of saidmotor.